RFR: 8376666: Convert G1BlockOffsetTable to use Atomic<T> [v2]

[Thomas Schatzl]

> Hi all,
> 
>   please review this conversion of the G1 block offset table to use `Atomic<T>`.
> 
> Testing: tier1-5, gha

Thomas Schatzl has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains three additional commits since the last revision:

 - * only change G1 BOT for now
 - Merge branch 'master' into 8376666-convert-bot
 - 8376666
   
   Hi all,
   
     please review this conversion of the various block offset tables to use `Atomic<T>`. Since they are very similar, and mostly changes from `uint8*` to `Atomic<uint8>*` I merged the conversion together.
   
   It is not the goal to actually merge them into one class that all three collectors use.
   
   Testing: tier1-5, gha

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/29482/files
  - new: https://git.openjdk.org/jdk/pull/29482/files/cb652fe6..4d588b78

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=29482&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=29482&range=00-01

  Stats: 45066 lines in 593 files changed: 20652 ins; 15837 del; 8577 mod
  Patch: https://git.openjdk.org/jdk/pull/29482.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/29482/head:pull/29482

PR: https://git.openjdk.org/jdk/pull/29482